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diff --git a/buch/papers/parzyl/images/halfplane.pov b/buch/papers/parzyl/images/halfplane.pov
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+//
+// 3dimage.pov
+//
+// (c) 2022 Prof Dr Andreas Müller
+//
+#version 3.7;
+#include "colors.inc"
+#include "skies.inc"
+#include "common.inc"
+
+global_settings {
+        assumed_gamma 1
+}
+
+#declare imagescale = 0.63;
+#declare ar = 0.02;
+
+#declare Cameracenter = <5,3,-4>;
+#declare Worldpoint = <0,-0.80, 0>;
+#declare Lightsource = < 7,10,-3>;
+#declare Lightdirection = vnormalize(Lightsource - Worldpoint);
+#declare Lightaxis1 = vnormalize(vcross(Lightdirection, <0,1,0>));
+#declare Lightaxis2 = vnormalize(vcross(Lightaxis1, Lightdirection));
+
+camera {
+	location Cameracenter
+	look_at Worldpoint
+	right 16/9 * x * imagescale
+	up y * imagescale
+}
+
+light_source {
+	Lightsource color White
+	area_light Lightaxis1 Lightaxis2, 10, 10
+	adaptive 1
+	jitter
+}
+
+sky_sphere {
+	pigment {
+		color White
+	}
+}
+
+arrow( <-2.1, 0,   0 >, < 2.2, 0,   0 >, ar, White)
+arrow( < 0,  -1.1, 0 >, < 0, 1.3, 0 >, ar, White)
+arrow( < 0,   0,  -2 >, < 0, 0,   2.2 >, ar, White)
+
+#declare planecolor = rgb<0.2,0.6,1.0>;
+#declare r = 0.01;
+
+#macro planebox()
+	box { <-2.1,-1.1,-2.1>, <0,1.1,2.1> }
+#end
+
+intersection {
+	plane { <0, 0,  1>, 0.001 }
+	plane { <0, 0, -1>, 0.001 }
+	planebox()
+	pigment {
+		color planecolor transmit 0.3
+	}
+	finish {
+		metallic
+		specular 0.95
+	}
+}
+
+#declare Xstep = 0.2;
+
+intersection {
+	union {
+		#declare X = 0;
+		#while (X > -2.5)
+			cylinder { <X,-3,0>, <X,+3,0>, r }
+			#declare X = X - Xstep;
+		#end
+
+		#declare Y = Xstep;
+		#while (Y < 2.5)
+			cylinder { <-3,  Y, 0>, <0,  Y, 0>, r }
+			cylinder { <-3, -Y, 0>, <0, -Y, 0>, r }
+			#declare Y = Y + Xstep;
+		#end
+	}
+	planebox()
+	pigment {
+		color planecolor
+	}
+	finish {
+		metallic
+		specular 0.95
+	}
+}
+
+#declare parammin = -4;
+#declare parammax = 4;
+#declare paramsteps = 100;
+#declare paramstep = (parammax - parammin) / paramsteps;
+
+#macro punkt(sigma, tau, Z)
+	<
+		0.5 * (tau*tau - sigma*sigma)
+		Z,
+		sigma * tau,
+	>
+#end
+
+#macro sigmasurface(sigma, farbe)
+	#declare taumin1 = 2/sigma;
+	#declare taumin2 = sqrt(4+sigma*sigma);
+	#if (taumin1 > taumin2)
+		#declare taumin = -taumin2;
+	#else
+		#declare taumin = -taumin1;
+	#end
+	
+	mesh {
+		#declare tau = taumin;
+		#declare taumax = -taumin;
+		#declare taustep = (taumax - taumin) / paramsteps;
+		#while (tau < taumax - taustep/2)
+			triangle {
+				punkt(sigma, tau,           -1),
+				punkt(sigma, tau,            0),
+				punkt(sigma, tau + taustep, -1)
+			}
+			triangle {
+				punkt(sigma, tau + taustep, -1),
+				punkt(sigma, tau + taustep,  0),
+				punkt(sigma, tau,            0)
+			}
+			#declare tau = tau + taustep;
+		#end
+		pigment {
+			color farbe
+		}
+		finish {
+			specular 0.9
+			metallic
+		}
+	}
+
+	union {
+		#declare tau = taumin;
+		#declare taumax = -taumin;
+		#declare taustep = (taumax - taumin) / paramsteps;
+		#while (tau < taumax - taustep/2)
+			sphere { punkt(sigma, tau, 0), r }
+			cylinder {
+				punkt(sigma, tau,           0),
+				punkt(sigma, tau + taustep, 0),
+				r
+			}
+			#declare tau = tau + taustep;
+		#end
+		sphere { punkt(sigma, tau, 0), r }
+		pigment {
+			color farbe
+		}
+		finish {
+			specular 0.9
+			metallic
+		}
+		
+	}
+#end
+
+#declare greensurfacecolor = rgb<0.6,1.0,0.6>;
+#declare redsurfacecolor = rgb<1.0,0.6,0.6>;
+
+sigmasurface(0.25, greensurfacecolor)
+sigmasurface(0.5,  greensurfacecolor)
+sigmasurface(0.75, greensurfacecolor)
+sigmasurface(1,    greensurfacecolor)
+sigmasurface(1.25, greensurfacecolor)
+sigmasurface(1.5,  greensurfacecolor)
+sigmasurface(1.75, greensurfacecolor)
+sigmasurface(2,    greensurfacecolor)
+
+union {
+	sigmasurface(0.25, redsurfacecolor)
+	sigmasurface(0.5,  redsurfacecolor)
+	sigmasurface(0.75, redsurfacecolor)
+	sigmasurface(1.00, redsurfacecolor)
+	sigmasurface(1.25, redsurfacecolor)
+	sigmasurface(1.5,  redsurfacecolor)
+	sigmasurface(1.75, redsurfacecolor)
+	sigmasurface(2,    redsurfacecolor)
+	rotate <0, 180, 0>
+}
+
+box { <-2,-1,-2>, <2,-0.99,2> 
+	pigment {
+		color rgb<1.0,0.8,0.6> transmit 0.8
+	}
+	finish {
+		specular 0.9
+		metallic
+	}
+}